FIG. 1 is a vertical cross-sectional view of a conventional scroll compressor disclosed in Japanese Patent Unexamined Publication No. 59-110893. A sealed container 30 houses a compression mechanism portion 31 at its upper portion and a motor 32 at its lower portion. The compression mechanism portion 31 includes a swirling spiral impeller portion 33 which performs swirling motion, and a fixed spiral impeller portion 34 meshed with the swirling spiral impeller portion 33 for compressing coolant gas. The fixed spiral impeller portion 34 is fixed to a bearing frame 35. A lower end of a crank shaft 36 which is formed integrally with a rotary shaft of the motor 32 is dipped into an oil stored in an oil reservoir 37 formed at the lower portion of the sealed container 30. An oil hole 38 is formed in the crank shaft 36. The lower end of the oil hole 38 is opened at the axis of the crank shaft 36, and the upper end thereof is opened at a position eccentric with respect to the axis of the rotary shaft. A communication hole 39 is provided in the swirling spiral impeller portion 33 at a position where the intermediate pressure between the suction and discharge pressures is obtained, and an intermediate pressure chamber 40 for the intermediate pressure is provided. A balance weight 41 is fixed to the crank shaft 36 within the intermediate pressure chamber 40. The swirling spiral impeller portion 33 is pressed against and thereby closely fitted to the fixed spiral impeller portion 34 due to the difference between the intermediate pressure and the internal pressure of the compressor. As the discharge pressure in the sealed container is higher than the internal pressure in the intermediate pressure chamber 40, the lubricant oil is pushed up through the oil hole 38 in the crank shaft 36 also due to the pressure difference and supplied to a sliding portion of the compressor. Thereafter, the lubricant oil is discharged into the intermediate pressure chamber 40. An oil reservoir portion 42 is provided in the bearing portion 35 which forms a part of the intermediate pressure chamber 40 so as to allow the lubricant oil discharged into the intermediate pressure chamber 40 to be readily stored temporarily. The oil reservoir portion 42 has an oil hole 43. The lubricant oil is led to the outside of the compressor from the oil hole 43 and through an oil pipe 44, cooled by cooling fins 45 and then led to an oil hole 46 provided in the fixed spiral impeller portion 34. The oil hole 46 provided in the fixed spiral impeller portion 34 is opened into a portion whose pressure is lower than that in the intermediate pressure chamber 40. The lubricant oil discharged into the intermediate pressure chamber 40 is discharged into the portion whose pressure is lower than that of the intermediate pressure chamber 40 from the oil hole 46 due to the pressure difference.
However, in the compressor arranged in the manner described above, the lubricant oil stored in the lubricant oil reservoir is led from the lower portion of the sealed container due to the pressure difference. An air conditioner is under various types of pressure conditions during the actual operation, and the amount of lubricant oil stored in the lubricant oil reservoir is thus not stable. Consequently, the amount of lubricant oil supplied to the compressing portion is not stable, and the performance of the compressor is thus varied greatly.